Masthead: the one format that names a shape
A masthead is a reserved, bought-in-advance placement at the top of a surface. It autoplays without sound for a short window, and its definition names an aspect ratio, which almost no other video ad format does. As of 2026-09-12.
| Property | What the definition states | Why it is unusual |
|---|---|---|
| Aspect ratio | Widescreen | Almost no other video format names one |
| Autoplay window | A short stretch, without sound | The message has to work silently |
| Availability | Reservation rather than auction | Booked ahead, so the spec is known early |
Inclusion rule. Properties the format definition states. Pricing and availability mechanics are outside the fit question these sheets ask. Order. The property that makes the format distinctive first.
1A named shape changes which column blocks the work
Most video ad formats leave shape to the surface, so the only thing a generator has to satisfy is a length. Here a shape is part of the format, and a tool that publishes no shape cannot be confirmed against it from its own page.
That is why a shape column in a register of generators is worth keeping even though most pages leave it empty. There is at least one format where the empty cell is the blocking one.
2Silent autoplay is a creative specification
Sound off by default means the picture carries everything: the product, the offer and any words that matter. A piece built around a voice track arrives with nothing to say.
For generated work that is not obviously a disadvantage, since a generated voice is often the weakest part of a piece. It does mean burned-in copy has to sit inside whatever the safe area of the surface turns out to be.
3An autoplay window behaves like a ceiling
The window is how long the piece plays before the surface moves on, so material past it is generated and never seen. Practically it is a length limit with a different name.
Where that window matches a common clip ceiling, the whole placement is one generation and no continuity question arises. That coincidence is worth checking, because it is the difference between a single call and an assembly.
A vocabulary entry: the definition, plus how the specification pages on these sheets usually publish it. Table checked 2026-09-12. Nearby entries: In-feed video, Impression.
4From brief to placement
For ad work around “Masthead”, SceneMixer's pages explain how its ad projects are produced:
Character sheets are always portrait and scene images always widescreen, whatever ratio the videos use.
SceneMixer, Vertical 9:16 or Landscape 16:9 — “Will choosing 9:16 make my character images vertical?” (read 2026-10-13)
The layout follows the project's aspect ratio, which is set when the project starts.
SceneMixer, How the Episode Editor Lays Out Vertical (9:16) and Landscape (16:9) Projects — “Can I switch between the two layouts?” (read 2026-10-13)